How Purity Testing Works
Every vial carries the figure ≥99%. This page covers what that number measures, how it is arrived at and where its meaning ends.
What is the purity figure telling you?
It is a ratio: the share of everything the instrument detected in the sample that was the compound you wanted. A result of ≥99% means that, of every hundred parts detected, ninety-nine were the compound named on the label.
What method measures purity?
The method is high-performance liquid chromatography. As the sample is forced through a column, its components separate, each according to how strongly it holds on to the column material. Because they emerge at different times, a detector records each one as a peak, and purity is the area under the target peak measured against the combined area of every peak.
What can an HPLC purity result tell you?
| Question | Does this test answer it? |
|---|---|
| Is the sample dominated by one component? | Yes |
| What share of the detected material does it make up? | Yes |
| Is it the compound named on the label? | No. Identity needs a separate measurement, usually mass spectrometry |
| Is there residual water, salt or solvent? | No, that is assessed separately |
| What material does it apply to? | The batch the sample came from |
Is identity confirmed as well as purity?
We will if you ask. Raise it before placing an order and we will let you know what is held on file for the stock going out at the moment.
How Purity Testing Works questions
What does a ≥99% purity figure mean?
That at least 99% of the total peak area detected by HPLC belonged to the target compound.
Does a purity result prove the compound matches the label?
No. A purity figure shows only that a single component dominates the sample. Establishing which component that is calls for a different measurement, typically mass spectrometry.
How is the purity of a peptide measured?
By high-performance liquid chromatography. The column splits the sample into its parts, each appearing as a separate peak, and purity compares the target peak with the total.
Is the purity figure specific to my vial?
It applies to the batch the certificate was issued for. Ask us, and we will send the certificate that matches the material in your vial.